We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 $M_{\rm Jup}$; 1.46 $R ... [more ▼]

We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 $M_{\rm Jup}$; 1.46 $R_{\rm Jup}$) in a 4.9-day, near-aligned ($\lambda = 8.1 \pm 3.6^\circ$) orbit around CD-24 102 ($V$=10.7; F9). WASP-28b is an inflated, Jupiter-mass planet (0.91 $M_{\rm Jup}$; 1.21 $R_{\rm Jup}$) in a 3.4-day, near-aligned ($\lambda = 8 \pm 18^\circ$) orbit around a $V$=12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars ($7^{+2}_{-1}$ Gyr for WASP-20 and $5^{+3}_{-2}$ Gyr for WASP-28; both with $T_{\rm eff}$ < 6250 K), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars' spins via tidal dissipation. [less ▲]

in AAS/Division for Planetary Sciences Meeting Abstracts (2012, October 01)

Stellar occultations of a same star by both Pluto and Charon (double events) yield instantaneous relative positions of the two bodies projected in the plane of the sky, at 10km-level accuracy. Assuming a ... [more ▼]

Stellar occultations of a same star by both Pluto and Charon (double events) yield instantaneous relative positions of the two bodies projected in the plane of the sky, at 10km-level accuracy. Assuming a given pole orientation for Charon's orbit, double events provide the satellite plutocentric distance r at a given orbital longitude L (counted from the ascending node on J2000 mean equator), and finally, constraints on its orbit. A double event observed on 22 June 2008 provides r=19,564+/-14 km at L=153.483+/-0.071 deg. (Sicardy et al. 2011), while another double event observed on 4 June 2011 yields: r=19,586+/-15 km at L = 343.211+/-0.072 deg. (all error bars at 1-sigma level). These two positions are consistent with a circular orbit for Charon, with a semi-major axis of a=19,575+\-10 km. This can be compared to the circular orbit found by Buie et al. (2012), based on Hubble Space Telescope data, with a=19,573+/-2 km. The 4 June 2011 stellar occultation provides 3 chords across Charon, from which a radius of Rc= 602.4+/-1.6 km is derived. This value can be compared to that obtained from the 11 July 2005 occultation: Rc= 606.0+/-1.5 km (Person et al. 2006) and Rc= 603.6+/-1.4 km (Sicardy et al. 2006). A third double event, observed on 23 June 2011 is under ongoing analysis, and will be presented. Buie et al. (2012), AJ 144, 15-34 (2012) Person et al, AJ 132, 1575-1580 (2006) Sicardy et al., Nature 439, 52-54 (2006) Sicardy et al., AJ 141, 67-83 (2011) B.S. thanks ANR "Beyond Neptune II". L.A.Y. acknowledges support by NASA, New Horizons and National Geographic grants. We thank B. Barnard, M.J. Brucker, J. Daily, C. Erikson, W. Fukunaga, C. Harlinten, C. Livermore, C. Nance, J.R. Regester, L. Salas, P. Tamblyn, R. Westhoff for help in the observations. [less ▲]

We report the discovery of two new transiting planets from the WASP survey. WASP-42 b is a 0.500 +- 0.035 M_J planet orbiting a K1 star at a separation of 0.0548 +- 0.0017 AU with a period of 4.9816872 ... [more ▼]

We report the discovery of two new transiting planets from the WASP survey. WASP-42 b is a 0.500 +- 0.035 M_J planet orbiting a K1 star at a separation of 0.0548 +- 0.0017 AU with a period of 4.9816872 +- 0.0000073 days. The radius of WASP-42 is 1.080 +- 0.057 R_J while its equilibrium temperature is T_eq = 995 +- 34 K. We detect some evidence of a small but non-zero eccentricity of e = 0.060 +- 0.013. WASP-49 b is a 0.378 +- 0.027 M_J planet around an old G6 star. It has a period of 2.7817387 +- 5.6 x 10-6 days and a separation of 0.0379 +- 0.0011 AU. This planet is slightly bloated, having a radius of 1.115 +- 0.056 R_J and an equilibrium temperature of T_eq = 1369 +- 42 K. Both planets have been followed up intensively in photometry, in total we have obtained 5 full and one partial transit light curves of WASP-42 and 4 full and one partial light curves of WASP-49 using the Euler-Swiss, TRAPPIST and Faulkes South telescopes. [less ▲]

Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the ... [more ▼]

Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the companion signal to be extracted. <BR /> Aims: MOA 2009-BLG-411 was detected on August 5, 2009 by the MOA-Collaboration. Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. <BR /> Methods: Thanks to observations by all the collaborations, this event was well monitored. We first decided to characterize the source star properties by using a more refined method than the classical one: we measure the interstellar absorption along the line of sight in five different passbands (VIJHK). Secondly, we model the lightcurve by using the standard technique: make (s,q,α) grids to look for local minima and refine the results by using a downhill method (Markov chain Monte Carlo). Finally, we use a Galactic model to estimate the physical properties of the lens components. <BR /> Results: We find that the source star is a giant G star with radius 9 R[SUB]&sun;[/SUB]. The grid search gives two local minima, which correspond to the theoretical degeneracy s ≡ s[SUP]-1[/SUP]. We find that the lens is composed of a brown dwarf secondary of mass M[SUB]S[/SUB] = 0.05 M[SUB]&sun;[/SUB] orbiting a primary M-star of mass M[SUB]P[/SUB] = 0.18 M[SUB]&sun;[/SUB]. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries. <BR /> Conclusions: As far as we are aware, this is the first detection using the microlensing technique of a binary system in our Galaxy composed of an M-star and a brown dwarf. Appendix is available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

We report the detection of WASP-35b, a planet transiting a metal-poor ([Fe/H] = -0.15) star in the Southern hemisphere, WASP-48b, an inflated planet which may have spun-up its slightly evolved host star ... [more ▼]

We report the detection of WASP-35b, a planet transiting a metal-poor ([Fe/H] = -0.15) star in the Southern hemisphere, WASP-48b, an inflated planet which may have spun-up its slightly evolved host star of 1.75 R_sun in the Northern hemisphere, and the independent discovery of HAT-P-30b / WASP-51b, a new planet in the Northern hemisphere. Using WASP, RISE, FTS and TRAPPIST photometry, with CORALIE, SOPHIE and NOT spectroscopy, we determine that WASP-35b has a mass of 0.72 +/- 0.06 M_J and radius of 1.32 +/- 0.03 R_J, and orbits with a period of 3.16 days, WASP-48b has a mass of 0.98 +/- 0.09 M_J, radius of 1.67 +/- 0.08 R_J and orbits in 2.14 days, while WASP-51b, with an orbital period of 2.81 days, is found to have a mass of 0.76 +/- 0.05 M_J and radius of 1.42 +/- 0.04 R_J, agreeing with values of 0.71 +/- 0.03 M_J and 1.34 +/- 0.07 R_J reported for HAT-P-30b. [less ▲]

We report the discovery of the low-density, transiting giant planet WASP-31b. The planet is 0.47 Jupiter masses and 1.56 Jupiter radii. It is in a 3.4-day orbit around a 1-Gyr-old, late-F-type, V = 11.7 ... [more ▼]

We report the discovery of the low-density, transiting giant planet WASP-31b. The planet is 0.47 Jupiter masses and 1.56 Jupiter radii. It is in a 3.4-day orbit around a 1-Gyr-old, late-F-type, V = 11.7 star, which is a member of a common proper motion pair. In terms of its low density, WASP-31b is second only to WASP-17b, which is a more highly irradiated planet of similar mass. [less ▲]

in Publications of the Astronomical Society of the Pacific [=PASP] (2011), 123

We report the discovery of a transiting planet with an orbital period of 3.05d orbiting the star TYC 7247-587-1. The star, WASP-41, is a moderately bright G8V star (V=11.6) with a metallicity close to ... [more ▼]

We report the discovery of a transiting planet with an orbital period of 3.05d orbiting the star TYC 7247-587-1. The star, WASP-41, is a moderately bright G8V star (V=11.6) with a metallicity close to solar ([Fe/H]=-0.08+-0.09). The star shows evidence of moderate chromospheric activity, both from emission in the cores of the CaII H and K lines and photometric variability with a period of 18.3d and an amplitude of about 1%. The rotation period of the star implies a gyrochronological age for WASP-41 of 1.8Gyr with an error of about 15%. We have used a combined analysis of the available photometric and spectroscopic data to derive the mass and radius of the planet (0.93+-0.06M_Jup, 1.21+-0.06R_Jup). Further observations of WASP-41 can be used to explore the connections between the properties of hot Jupiter planets and the level of chromospheric activity in their host stars. [less ▲]

Since 2006 WASP-South has been scanning the Southern sky for transiting exoplanets. Combined with Geneva Observatory radial velocities we have so far found over 30 transiting exoplanets around relatively ... [more ▼]

Since 2006 WASP-South has been scanning the Southern sky for transiting exoplanets. Combined with Geneva Observatory radial velocities we have so far found over 30 transiting exoplanets around relatively bright stars of magnitude 9-13. We present a status report for this ongoing survey. [less ▲]

We report the discovery of WASP-34b, a sub-Jupiter-mass exoplanet transiting its 10.4-magnitude solar-type host star (1SWASP J110135.89-235138.4; TYC 6636-540-1) every 4.3177 days in a slightly eccentric ... [more ▼]

We report the discovery of WASP-34b, a sub-Jupiter-mass exoplanet transiting its 10.4-magnitude solar-type host star (1SWASP J110135.89-235138.4; TYC 6636-540-1) every 4.3177 days in a slightly eccentric orbit (e = 0.038 +/- 0.012). We find a planetary mass of 0.59 +/- 0.01 M_Jup and radius of 1.22 ^{+0.11}_{-0.08} R_Jup. There is a linear trend in the radial velocities of 55+/-4 m/s/y indicating the presence of a long-period third body in the system with a mass > 0.45 M_Jup at a distance of >1.2 AU from the host star. This third-body is either a low-mass star, white dwarf, or another planet. The transit depth ((R_P/R_*)^2 = 0.0126) and high impact parameter (b = 0.90) suggest that this could be the first known transiting exoplanet expected to undergo grazing transits, but with a confidence of only ~80%. [less ▲]

in Monthly Notices of the Royal Astronomical Society (2011), 410(3), 16311636

We report the detection of a 0.6 M-J extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76d. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE ... [more ▼]

We report the detection of a 0.6 M-J extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76d. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE spectroscopy yields a planet of R[SUB]p[/SUB] = 1.22 R[SUB]J[/SUB] and M[SUB]p[/SUB] = 0.58 M[SUB]J[/SUB] around a slightly metal-poor solar-type host star, [Fe/H] = - 0.05 +/- 0.10, of R[SUB]*[/SUB] = 0.92 R[SUB]solar[/SUB] and M[SUB]*[/SUB] = 1.00 M[SUB]solar[/SUB]. WASP-25b is found to have a density of ρ[SUB]p[/SUB] = 0.32 ρ[SUB]J[/SUB], a low value for a sub-Jupiter mass planet. We investigate the relationship of planetary radius to planetary equilibrium temperature and host star metallicity for transiting exoplanets with a similar mass to WASP-25b, finding that these two parameters explain the radii of most low-mass planets well. [less ▲]

We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2 Gyr. We ... [more ▼]

We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2 Gyr. We derive a radius (0.89 ± 0.02 R Jup) for the companion that is consistent with that predicted (0.914 R Jup) by a model of a 1 Gyr old, non-irradiated BD with a dusty atmosphere. The location of WASP-30b in the minimum of the mass-radius relation is consistent with the quantitative prediction of Chabrier & Baraffe, thus confirming the theory. [less ▲]

We report the discovery of a transiting planet orbiting the star TYC 6446-326-1. The star, WASP-22, is a moderately bright (V = 12.0) solar-type star (T[SUB]eff[/SUB] = 6000 ± 100 K, [Fe/H] = –0.05 ± 0.08). The light curve of the star obtained with the WASP-South instrument shows periodic transit-like features with a depth of about 1% and a duration of 0.14 days. The presence of a transit-like feature in the light curve is confirmed using z-band photometry obtained with Faulkes Telescope South. High-resolution spectroscopy obtained with the CORALIE and HARPS spectrographs confirms the presence of a planetary mass companion with an orbital period of 3.533 days in a near-circular orbit. From a combined analysis of the spectroscopic and photometric data assuming that the star is a typical main-sequence star we estimate that the planet has a mass M [SUB]p[/SUB] = 0.56 ± 0.02M [SUB]Jup[/SUB] and a radius R [SUB]p[/SUB] = 1.12 ± 0.04R [SUB]Jup[/SUB]. In addition, there is a linear trend of 40 m s[SUP]–1[/SUP] yr[SUP]–1[/SUP] in the radial velocities measured over 16 months, from which we infer the presence of a third body with a long-period orbit in this system. The companion may be a low mass M-dwarf, a white dwarf, or a second planet. [less ▲]

We report the discovery of a Saturn-sized planet transiting a V = 11.3, K4 dwarf star every 3.9 days. WASP-29b has a mass of 0.24 ± 0.02 M [SUB]Jup[/SUB] and a radius of 0.79 ± 0.05 R [SUB]Jup[/SUB], making it the smallest planet so far discovered by the WASP survey, and the exoplanet most similar in mass and radius to Saturn. The host star WASP-29 has an above-solar metallicity and fits a possible correlation for Saturn-mass planets such that planets with higher-metallicity host stars have higher core masses and thus smaller radii. [less ▲]

We report the discovery of a transiting planet orbiting the star TYC 2-1155-1. The star, WASP-32, is a moderately bright (V=11.3) solar-type star (Teff=6100 +- 100K, [Fe/H] = -0.13 +- 0.10). The lightcurve of the star obtained with the WASP-South and WASP-North instruments shows periodic transit-like features with a depth of about 1% and a duration of 0.10d every 2.72d. The presence of a transit-like feature in the lightcurve is confirmed using z-band photometry obtained with Faulkes Telescope North. High resolution spectroscopy obtained with the CORALIE spectrograph confirms the presence of a planetary mass companion. From a combined analysis of the spectroscopic and photometric data, assuming that the star is a typical main-sequence star, we estimate that the planet has a mass M_p = 3.60 +- 0.07 M_Jup and a radius R_p = 1.19 +- 0.06R_Jup. WASP-32 is one of a small group of hot Jupiters with masses M_p > 3M_Jup. We find that some stars with hot Jupiter companions and with masses M_* =~ 1.2M_sun, including WASP-32, are depleted in lithium, but that the majority of these stars have similar lithium abundances to field stars. [less ▲]

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer ... [more ▼]

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer an effective temperature T [SUB]eff[/SUB] = 6075 ± 100 K and a surface gravity of log g = 4.15 ± 0.10. A comparison of these parameters with theoretical isochrones and evolutionary mass tracks places only weak constraints on the age of the host star, which we estimate to be 3.8[SUP]+1.3[/SUP] [SUB]-1.2[/SUB] Gyr. The planetary nature of the companion was confirmed by radial velocity measurements and additional photometric observations. These data were fit simultaneously in order to determine the most probable parameter set for the system, from which we infer a planetary mass of 1.071[SUP]+0.036[/SUP] [SUB]-0.038[/SUB] M [SUB]Jup[/SUB] and radius 1.3[SUP]+0.039[/SUP] [SUB]-0.037[/SUB] R [SUB]Jup[/SUB]. [less ▲]

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We ... [more ▼]

Context. Not only is gravitational microlensing a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. <BR ... [more ▼]

Context. Not only is gravitational microlensing a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. <BR /> Aims: In high-magnification events, the lens caustic may cross over the source disk, which allows determination of the angular size of the source and measurement of its limb darkening. <BR /> Methods: When such extended-source effects appear close to maximum magnification, the resulting light curve differs from the characteristic Paczyński point-source curve. The exact shape of the light curve close to the peak depends on the limb darkening of the source. Dense photometric coverage permits measurement of the respective limb-darkening coefficients. <BR /> Results: In the case of the microlensing event OGLE 2008-BLG-290, the K giant source star reached a peak magnification at about 100. Thirteen different telescopes have covered this event in eight different photometric bands. Subsequent light-curve analysis yielded measurements of linear limb-darkening coefficients of the source in six photometric bands. The best-measured coefficients lead to an estimate of the source effective temperature of about 4700[SUP]+100[/SUP][SUB]-200[/SUB] K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200 ± 100 K. <BR /> Conclusions: Because the limb-darkening measurements, at least in the CTIO/SMARTS2 V_s- and I_s-bands, are among the most accurate obtained, the above disagreement needs to be understood. A solution is proposed, which may apply to previous events where such a discrepancy also appeared. [less ▲]

We report the discovery of WASP-26b, a moderately over-sized Jupiter-mass exoplanet transiting its 11.3-magnitude early-G-type host star (1SWASP J001824.70-151602.3; TYC 5839-876-1) every 2.7566 days. A simultaneous fit to transit photometry and radial-velocity measurements yields a planetary mass of 1.02 +/- 0.03 M_Jup and radius of 1.32 +/- 0.08 R_Jup. The host star, WASP-26, has a mass of 1.12 +/- 0.03 M_sun and a radius of 1.34 +/- 0.06 R_sun and is in a visual double with a fainter K-type star. The two stars are at least a common-proper motion pair with a common distance of around 250 +/- 15 pc and an age of 6 +/- 2 Gy. [less ▲]

We report the discovery of the transiting giant planet WASP-17b, the least-dense planet currently known. It is 1.6 Saturn masses but 1.5-2 Jupiter radii, giving a density of 6-14 per cent that of Jupiter ... [more ▼]

We report the discovery of the transiting giant planet WASP-17b, the least-dense planet currently known. It is 1.6 Saturn masses but 1.5-2 Jupiter radii, giving a density of 6-14 per cent that of Jupiter. WASP-17b is in a 3.7-day orbit around a sub-solar metallicity, V = 11.6, F6 star. Preliminary detection of the Rossiter-McLaughlin effect suggests that WASP-17b is in a retrograde orbit (lambda ~ -150 deg), indicative of a violent history involving planet-planet or planet-star scattering. WASP-17b's bloated radius could be due to tidal heating resulting from recent or ongoing tidal circularisation of an eccentric orbit, such as the highly eccentric orbits that typically result from scattering interactions. It will thus be important to determine more precisely the current orbital eccentricity by further high-precision radial velocity measurements or by timing the secondary eclipse, both to reduce the uncertainty on the planet's radius and to test tidal-heating models. Owing to its low surface gravity, WASP-17b's atmosphere has the largest scale height of any known planet, making it a good target for transmission spectroscopy. [less ▲]

We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass M [SUB]pl[/SUB] = 1.15 Â± 0.08 M[SUB]J[/SUB] , radius R [SUB]pl[/SUB] = 1.31 Â± 0.06 R[SUB]J[/SUB] , and orbital period P = 0.7888399 Â± 0.0000008 days. Through spectroscopic analysis, we determine the host star to be a slightly super-solar metallicity ([M/H] = 0.1 Â± 0.1 dex) G-dwarf with T [SUB]eff[/SUB] = 5500 Â± 100 K. In addition, we detect periodic, sinusoidal flux variations in the light curve which are used to derive a rotation period for the star of P [SUB]rot[/SUB] = 10.5 Â± 0.2 days. The relatively short stellar rotation period suggests that either WASP-19 is somewhat young (~ 600 Myr old) or tidal interactions between the two bodies have caused the planet to spiral inward over its lifetime resulting in the spin-up of the star. Due to the detection of the rotation period, this system has the potential to place strong constraints on the stellar tidal quality factor, Q'[SUB] s [/SUB], if a more precise age is determined. [less ▲]